1. Field of the Invention
The present invention relates to a liquid ejection head substrate used in a liquid ejection head that ejects liquid, and to a liquid ejection head.
2. Description of the Related Art
In general, regarding inkjet print heads (hereinafter, also called “print heads”), which are representative examples of liquid ejection heads, the viscosity of ink used for printing increases as ambient temperature decreases. Hence, when a print head is used in environments with very low temperatures, there may be a case where the volume of ink ejected from the print head is decreased (variations in ejection volume) or ink is not ejected normally (defective ejection). In this case, in images obtained by printing, uneven density due to variations in ejection volume, unfavorable dot shapes due to defective ejection, or the like is observed. To solve these problems, control is performed in such a manner that the print head is heated before or during printing operations so as to be in a predetermined temperature range, thereby regulating temperature distribution.
Examples of known configurations for the above-described control include a configuration in which heat generating elements (hereinafter also called “heating elements”) for heat application are provided on an inkjet print head substrate (hereinafter, also called a “substrate”). By driving these heating elements, the temperatures of the substrate and ink within the substrate are adjusted.
In International Publication No. 2012/044299, as illustrated in FIG. 2 thereof, a configuration is disclosed in which an ink supply port having a shape extending along ejection port arrays are provided in the center of the substrate, and a plurality of temperature detection elements and a plurality of heating elements are provided for the ejection ports arranged on both sides of the ink supply port. With this configuration, regions having a low temperature can be selectively heated using the heating elements, by detecting the temperature distribution of the substrate using the temperature detection elements.
However, in International Publication No. 2012/044299, since the temperature detection elements and the heating elements are provided for each of the ejection port arrays, the numbers of the temperature detection elements and the heating elements are increased when the number of the ejection port arrays is increased to increase the number of colors and enhance image quality. As a result, a larger space in which to arrange the temperature detection elements, heating elements, and drive circuits for driving these elements is required, thereby causing increases in the area of the substrate and the manufacturing cost of the substrate. Since it is more advantageous when the number of the printing elements in the ejection port array is larger from the viewpoint of obtaining a higher speed and higher quality, it is preferable to decrease the length of the substrate in a direction perpendicular to the direction in which the ejection port arrays extend, thereby suppressing an increase in the area of the substrate, to realize a higher speed and higher quality together with suppression of the manufacturing cost.
On the other hand, when the temperature detection elements and heating elements are not provided for each ejection port array, since the substrate is partitioned by the supply port having a shape extending in the direction in which the ejection port arrays extend, it is difficult to sufficiently heat the regions on the two sides of the supply port. Hence, it becomes difficult to regulate the temperature distribution of the substrate.
Further, when the temperature detection elements and the heating elements are arranged close to each other, as in International Publication No. 2012/044299, the temperatures of regions heated by the heating elements are detected and, hence, the accuracy of temperature detection, which is the base of temperature control of the heating elements, is decreased, whereby it becomes difficult to regulate the temperature distribution over the whole substrate.